18428 Federal Register / Vol. 72, No. 70 / Thursday, April 12, 2007 / Proposed Rules 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R04–OAR–2005–AL–0002–200623; 

FRL–8298–1] 

Approval and Promulgation of 

Implementation Plans: Alabama: 

Proposed Approval of Revisions to the 

Visible Emissions Rule 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: EPA is proposing to approve 

the Visible Emissions portion of the 

State Implementation Plan (SIP) 

revision submitted to EPA, by the 

Alabama Department of Environmental 

Management (ADEM), on September 11, 

2003 (the ‘‘2003 ADEM submittal’’), 

provided it is revised as described in 

this action and submitted as a SIP 

revision. The open burning portion of 

the submittal was previously approved 

in a separate action on March 9, 2006 

(71 FR 12138). 

DATES: Comments must be received on 

or before June 11, 2007. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R04–

OAR–2005–AL–0002, by one of the 

following methods: 

(a) www.regulations.gov: Follow the 

on-line instructions for submitting 

comments. 

(b) E-mail: harder.stacy@epa.gov. 

(c) Fax: 404–562–9019. 

(d) Mail: ‘‘EPA–R04–OAR–2005–AL–

0002,’’ Regulatory Development Section, 

Air Planning Branch, Air, Pesticides and 

Toxics Management Division, U.S. 

Environmental Protection Agency, 

Region 4, 61 Forsyth Street, SW., 

Atlanta, Georgia 30303–8960. 

(e) Hand Delivery or Courier: Stacy 

Harder, Regulatory Development 

Section, Air Planning Branch, Air, 

Pesticides and Toxics Management 

Division, 12th floor, U.S. Environmental 

Protection Agency, Region 4, 61 Forsyth 

Street, SW., Atlanta, Georgia 30303–

8960. Such deliveries are only accepted 

during the Regional Office’s normal 

hours of operation. The Regional 

Office’s official hours of business are 

Monday through Friday, 8:30 to 4:30, 

excluding federal holidays. 

Instructions: Direct your comments to 

Docket ID No. ‘‘EPA–R04–OAR–2005–

AL–0002.’’ EPA’s policy is that all 

comments received will be included in 

the public docket without change and 

may be made available online at 

http://www.regulations.gov, including 

any personal information provided, 

unless the comment includes 

information claimed to be Confidential 

Business Information (CBI) or other 

information whose disclosure is 

restricted by statute. Do not submit 

through www.regulations.gov or e-mail, 

information that you consider to be CBI 

or otherwise protected. The 

www.regulations.gov Web site is an 

‘‘anonymous access’’ system, which 

means EPA will not know your identity 

or contact information unless you 

provide it in the body of your comment. 

If you send an e-mail comment directly 

to EPA without going through 

www.regulations.gov, your e-mail 

address will be automatically captured 

and included as part of the comment 

that is placed in the public docket and 

made available on the Internet. If you 

submit an electronic comment, EPA 

recommends that you include your 

name and other contact information in 

the body of your comment and with any 

disk or CD–ROM you submit. If EPA 

cannot read your comment due to 

technical difficulties and cannot contact 

you for clarification, EPA may not be 

able to consider your comment. 

Electronic files should avoid the use of 

special characters, any form of 

encryption, and be free of any defects or 

viruses. For additional information 

about EPA’s public docket visit the EPA 

Docket Center homepage at http:// 

www.epa.gov/epahome/dockets.htm. 

Docket: All documents in the 

electronic docket are listed in the 

www.regulations.gov index. Although 

listed in the index, some information is 

not publicly available, i.e., CBI or other 

information whose disclosure is 

restricted by statute. Certain other 

material, such as copyrighted material, 

is not placed on the Internet and will be 

publicly available only in hard copy 

form. Publicly available docket 

materials are available either 

electronically in www.regulations.gov 

or in hard copy at the Regulatory 

Development Section, Air Planning 

Branch, Air, Pesticides and Toxics 

Management Division, U.S. 

Environmental Protection Agency, 

Region 4, 61 Forsyth Street, SW., 

Atlanta, Georgia 30303–8960. EPA 

requests that if at all possible, you 

contact the person listed in the FOR

FURTHER INFORMATION CONTACT section to 

schedule your inspection. The Regional 

Office’s official hours of business are 

Monday through Friday, 8:30 to 4:30, 

excluding legal holidays. 

FOR FURTHER INFORMATION CONTACT: 

Stacy Harder, Regulatory Development 

Section, Air Planning Branch, Air, 

Pesticides and Toxics Management 

Division, U.S. Environmental Protection 

Agency, Region 4, 61 Forsyth Street, 

SW., Atlanta, Georgia 30303–8960. The 

telephone number is (404) 562–9042. 

Ms. Harder can also be reached via 

electronic mail at harder.stacy@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Table of Contents 

I. What Action Is EPA Proposing? 

II. Why Is EPA Proposing This Action? 

III. What Is the Rationale for This SIP 

Revision? 

IV. What Does the Visible Emissions Rule in 

the Current SIP Require, and What 

Changes Are Requested by ADEM? 

V. What Changes Does EPA Recommend to 

the Submittal? 

VI. What Technical Analysis Was Used To 

Support Approval of This SIP Revision? 

VII. What Happens Next? 

VIII. Proposed Action 

IX. Statutory and Executive Order Reviews 

I. What Action Is EPA Proposing? 

EPA is proposing an approval, under 

Section 110(k) of the Clean Air Act 

(CAA), of the Visible Emissions portion 

of the Alabama SIP revision submitted 

on September 11, 2003. This proposed 

approval is contingent upon Alabama 

submitting a revised SIP submission 

addressing EPA’s concerns regarding 

impacts of the rule changes on 

attainment of the National Ambient Air 

Quality Standards (NAAQS). Because 

the necessary revisions would 

materially alter both the existing SIP 

approved rule and the submitted 

revision, the State must make a SIP 

submittal to effect the changes noted by 

EPA below. As with any SIP revision, 

the State must provide public notice of 

and a public hearing on the proposed 

changes. If, after consideration of public 

comments, EPA determines the revised 

SIP submission meets the requirements 

of the CAA and is consistent with the 

recommended changes outlined in this 

action, the Agency may proceed to 

publish its approval of the revised SIP 

in the Federal Register. Alabama’s 

revised submittal must be consistent 

with the changes discussed in this 

action for EPA to approve its 

incorporation into the SIP. If the revised 

language does not conform specifically 

to the recommended changes, EPA will 

need to re-evaluate Alabama’s submittal 

and, if the changes are approvable, repropose approval of the SIP submittal. 

II. Why Is EPA Proposing This Action? 

EPA is taking this action in response 

to a request from ADEM to revise the 

Visible Emissions portion of Alabama’s 

SIP rule pertaining to sources of 

particulate matter (PM) emissions. The 

request, submitted to EPA on September 

11, 2003, would revise Alabama SIP rule 

335–3–4–.01 (‘‘Visible Emissions’’) by 

amending the requirements for units 


rmajette on PROD1PC67 with PROPOSALS
Federal Register / Vol. 72, No. 70 / Thursday, April 12, 2007 / Proposed Rules 18429 

that operate continuous opacity 

monitoring systems (COMS) and that are 

not subject to any opacity limits other 

than those in rule 335–3–4–.01(1) 

(‘‘Visible Emissions Restrictions for 

Stationary Sources’’). 

Under section 110(l) of the CAA, EPA 

may not approve revisions to SIPs if the 

revisions would interfere with any 

applicable requirement concerning 

attainment and reasonable further 

progress (RFP), or any other applicable 

requirement of the CAA. In determining 

whether to approve a requested 

revision, EPA considers the relevant 

impacts of the proposed change in light 

of the type of requirement affected by 

the requested revision. In this instance, 

the State is proposing revisions to its 

opacity requirements. We define opacity 

as the degree to which emissions reduce 

the transmission of light and obscure 

the view of an object in the background. 

(See 40 CFR 60.2). 

A change in opacity standards may 

not necessarily impact on a State’s 

ability to meet the PM NAAQS or any 

other applicable requirement of the Act 

because, as discussed further in this 

action, a reliable and direct correlation 

between opacity and PM emissions 

cannot be established without 

significant site-specific simultaneous 

testing of both PM emissions and 

opacity, particularly for short-term 

periods (e.g., 24 hours or less). 

Nonetheless, because there is at least an 

indirect relationship between opacity 

and PM emissions, including the use of 

opacity to track the effectiveness of PM 

control equipment operation, we 

considered the impact of Alabama’s 

proposed revision on the NAAQS for 

PM10 and PM2.5, and on other 

applicable requirements. No changes are 

being proposed to revise the particulate 

mass limits in the Alabama SIP, and 

sources must continue to meet 

applicable emissions limits. EPA 

proposes to approve Alabama’s revision, 

with our recommended changes, 

because we determined that, with the 

changes specified in this action, the SIP 

revision will not interfere with 

attainment of either of the PM NAAQS 

or with other applicable requirements. 

III. What Is the Rationale for This SIP 

Revision? 

Monitoring opacity by use of COMS 

provides far more data than EPA 

Reference Method 9, the compliance 

determination method specified by most 

SIPs, including Alabama’s. Alabama 

adopted into the State’s regulations the 

rule revision contained in the 2003 

ADEM submittal on August 26, 2003, 

and has since operated under it as a 

State-only enforceable provision. The 

purpose of that rule revision was to 

make the State’s regulation consistent 

with what had been its practice in 

exercising enforcement discretion with 

respect to use of COMS data since the 

early 1980’s. 

In addition to requiring corrective 

actions and prompt reporting of 

deviations from permit terms, the State 

has other oversight procedures in place 

that ensure long, continuous periods of 

high opacity are properly addressed by 

the source. ADEM receives quarterly 

emissions reports from plants that 

utilize COMS, which indicate the 

opacity of the emissions from sources 

subject to this rule revision. ADEM 

reviews the information and determines 

if further action should be taken due to 

any opacity exceedances. The data is 

required to be in a format that includes 

source operating time, monitor 

operating time, exempt opacity 

exceedances, and non-exempt opacity 

exceedances. The reports include daily 

opacity exceedances as well as a 

summary of the data for the entire 

quarter. In these reports, the sources 

also calculate the percentage of 

operating time in which they had nonexempt opacity exceedances as well as 

the percentage of operating time with 

any (total of exempt and non-exempt) 

opacity exceedances. 

ADEM has developed a program that 

takes the summary data from the 

quarterly opacity reports and calculates 

the percentage of source operating time 

that the opacity of emissions from 

individual units (or multiple units with 

a common stack) exceeded the opacity 

standard due to non-exempt reasons 

during the calendar quarter. As a check 

on the quarterly calculations from the 

source, this program also calculates the 

percentage of operating time that the 

opacity of emissions from individual 

units exceeded the opacity standard for 

any reason. With this program, ADEM 

compares the performance of each unit 

to the historical performance of that unit 

as well as compares it to the 

performance of the other units at that 

plant and other similar plants in the 

State, and the performance of the unit 

to the two percent threshold in the 

Alabama submittal. If the performance 

of a unit is not consistent with its 

historical performance or the 

performance of other similar units in the 

State, ADEM can review the daily 

exceedances of the opacity standard for 

the unit in question to determine if the 

exceedances were sporadic, or grouped 

in consecutive hours or consecutive 

days. ADEM may also ask the company 

for a detailed explanation of the 

exceedances (or a subset of 

exceedances) during the calendar 

quarter. If, for a source subject to the 

new standard, the number of unexcused 

opacity exceedances is in excess of two 

percent of the source operating time for 

which the opacity standard was 

applicable during the quarter, formal 

enforcement action may proceed. 

Opacity limitations have typically 

accompanied periodic Reference 

Method 5 particulate matter compliance 

tests (Method 5 tests) in SIPs. That is, 

where Method 5 tests are used to 

demonstrate compliance with filterable 

PM mass emission limitations, opacity 

limits and associated monitoring are 

commonly used as an indirect monitor 

for PM emissions and as indicators of 

good PM control equipment operation 

during the periods between Method 5 

tests. EPA has long recognized opacity 

monitoring as a method of ensuring 

proper control device operation. See 39 

FR 9308, 9309 (Mar. 8, 1974) (NSPS 

Additions and Miscellaneous 

Amendments discussing opacity as an 

indicator of whether control equipment 

is properly maintained and operated). 

With use of continuous opacity 

monitors it is possible to have a 

continuous stream of opacity data. This 

results in the collection of many 

individual, short-term opacity 

measurements that reflect the full range 

of control device operating variability 

and, depending upon the amount of 

variability, may or may not be indicative 

of poor operation of control equipment 

and excess PM emissions. For example, 

coal-fired power generation facilities 

may experience sporadic opacity 

exceedances caused by variations in the 

constituents of coal burned. The revised 

Alabama rule shifts emphasis from 

isolated six-minute periods to longer 

periods that are more indicative of 

excess PM emissions and problems with 

operation and maintenance of control 

devices. As noted above, under the 

proposed revised rule, with the changes 

discussed in this action, an emissions 

unit is allowed: (1) Up to 100 percent 

opacity during periods of startup, 

shutdown, load change, and rate change 

or other short, intermittent periods upon 

terms approved by ADEM’s Director and 

included in a state-issued permit; (2) up 

to 100 percent opacity for up to two 

percent of the operating time on a 

quarterly basis (less the exempted 

periods approved by ADEM’s Director 

and included in a state-issued permit), 

for no more than 10 percent of the time 

on a daily basis; and (3) up to 20 percent 

opacity for the rest of the time in a 

quarter. EPA believes this approach, 

along with the monitoring and oversight 

safeguards discussed above, make 

appropriate use of COMS data for 

ensuring compliance with PM limits. 


rmajette on PROD1PC67 with PROPOSALS
18430 Federal Register / Vol. 72, No. 70 / Thursday, April 12, 2007 / Proposed Rules 

1Alabama Rule 335–3–4–.01, ‘‘Visible 

Emissions,’’ provides four specific ‘‘exceptions’’ to 

compliance with the generally applicable opacity 

limit at subparagraphs 335–3–4–.01(b), (c), (d), and 

(e). To be consistent with more common 

terminology, in this notice we refer to these as 

‘‘exemptions.’’

2Subparagraph (d) provides that ADEM’s Director 

may approve exceptions to this Rule in the form of 

source-specific adjustments to the opacity standard, 

provided certain conditions are met demonstrating 

to the Director’s satisfaction that, with the 

adjustment, the source would continue to comply 

with its SIP particulate matter mass emissions limit. 

3Subparagraph (e) provides that the provisions of 

this Rule do not apply to combustion sources in 

single-family and duplex dwellings where such 

sources are used for heating or other domestic 

purposes. 

IV. What Does the Visible Emissions 

Rule in the Current SIP Require, and 

What Changes Are Requested by 

ADEM? 

The subject Visible Emissions rule is 

in Chapter 335–3–4 (‘‘Control of 

Particulate Emissions’’) of the Alabama 

SIP. The currently approved Alabama 

Rule 335–3–4–.01, ‘‘Visible Emissions,’’

has a generally applicable limit of 20 

percent on opacity level and provides 

that one six-minute period per hour of 

up to 40 percent opacity is exempted 1

from the 20 percent limit. The Director 

of ADEM may also grant, as part of a 

permit issued by the State, exemptions 

to the 20 percent limit during startup, 

shutdown, load change and rate change 

or other short, intermittent periods that 

are in addition to the hourly six-minute 

40 percent exemption. These 

exemptions are provided by 

subparagraphs (1)(b) and (1)(c), 

respectively. Additional exemptions for 

circumstances not relevant to this 

rulemaking are provided by 

subparagraphs (1)(d) 2 and (1)(e).3 The 

text of the current rule reads, in relevant 

part, as follows: 

(1) Visible Emissions Restrictions for 

Stationary Sources. 

(a) Except as provided in subparagraphs 

(b), (c), (d), or (e) of this paragraph, no person 

shall discharge into the atmosphere from any 

source of emission, particulate of an opacity 

greater than that designated as twenty 

percent (20%) opacity, as determined by a six 

(6) minute average. 

(b) During one six (6) minute period in any 

sixty (60) minute period, a person may 

discharge into the atmosphere from any 

source of emission, particulate of an opacity 

not greater than that designated as forty 

percent (40%) opacity. 

(c) The Director may approve exceptions to 

this Rule or specific sources which hold 

permits under Chapter 335–3–14; provided 

however, such exceptions may be made for 

startup, shutdown, load change, and rate 

change or other short, intermittent periods of 

time upon terms approved by the Director 

and made a part of such permit. 

* * * * * 

(2) Compliance with opacity standards in 

this Rule shall be determined by conducting 

observations in accordance with Reference 

Method 9 in Appendix A, 40 CFR Part 60, as 

the same may be amended requiring a six (6) 

minute average as determined by twenty-four 

(24) consecutive readings, at intervals of 

fifteen (15) seconds each. 

The 2003 ADEM submittal would add 

three new paragraphs, (3), (4), and (5), 

to Alabama Rule 335–3–4–.01 that apply 

only to those emissions units that use 

COMS for measuring opacity, that 

operate such systems according to 

Federal specifications, and that are 

subject only to those opacity limits of 

the State’s SIP (e.g., not subject to 

opacity limits under any 

preconstruction permit or other 

regulation). The revision provides that 

these units will not be in violation of 

the State’s generally applicable opacity 

limitation if the non-exempt excess 

emissions periods do not exceed two 

percent of the source operating hours for 

which the opacity standard is applicable 

and for which the COMS is indicating 

valid data, on a quarterly basis. The text 

of the proposed change reads as follows: 

(3) The conditions in paragraph (4) of this 

Rule apply to each emissions unit that meets 

all of the following requirements: 

(a) A Continuous Opacity Monitoring 

System (COMS) is used for indication of 

opacity of emissions; 

(b) With respect to opacity limitations, the 

units are subject only to the opacity 

provisions stated in paragraph (1) of this 

Rule; and 

(c) The COMS system utilized is required 

to comply with the requirements of 40 CFR 

60.13 or 40 CFR 75.14 (if applicable) and is 

required to be certified in accordance with 

the requirements of 40 CFR 60, Appendix B, 

Performance Specification 1. 

(4) During each calendar quarter, the 

permittee will not be deemed in violation of 

Rule 335–3–4–.01(1) if the non-exempt 

excess emissions periods do not exceed 2.0 

percent of the source operating hours for 

which the opacity standard is applicable and 

for which the COMS is indicating valid data. 

(5) Nothing in paragraph (4) of this Rule 

shall be construed to supercede the validity 

of opacity readings taken under paragraph (2) 

of this Rule. 

In summary, under the 2003 

submission, sources operating COMS 

would not be deemed in violation of the 

standard where emissions in excess of 

the 20 percent opacity were limited to: 

(1) One six-minute average per hour of 

up to 40 percent opacity; (2) periods of 

startup, shutdown, load change and rate 

change or other short intermittent 

periods upon terms approved by 

ADEM’s Director and included in a 

State-issued permit; and (3) no more 

than two percent of the remaining 

operating time after subtracting out all 

periods qualifying under the previous 

two instances. 

V. What Changes Does EPA 

Recommend to the Submittal? 

As described above, under the 

Alabama SIP, Method 9 is the method 

specified for determining compliance 

with the 20 percent opacity limit. COMS 

are not specified as the method to 

determine compliance with the 

numerical opacity limit, although 

COMS data can be credible evidence of 

opacity. Opacity, both as measured by 

Method 9 and COMS, has been used as 

a proxy for particulate emissions and to 

indicate whether a company is 

following good air pollution control 

practices. ADEM has proposed 

amending its SIP to allow up to two 

percent of COMS readings to exceed 20 

percent opacity during non-exempt 

periods, in part since the Alabama SIP 

provides no other exemption from the 

standard for malfunction. 

The use of COMS increases data 

availability and provides a greater 

degree of reliability compared to the 

Method 9 procedure. Nonetheless, as 

currently written, the revision would 

allow a source to emit at a higher 

allowable average opacity percent level 

(as measured by COMS in six-minute 

increments) on a quarterly basis as well 

as allowing higher short term excursions 

than the current approved SIP allows. 

Because this potential for higher average 

opacity on a quarterly basis could 

indicate an increase in particulate 

matter emissions, and in the absence of 

a supporting demonstration of 

compliance with CAA requirements 

from the State, we believe that the 2003 

SIP submittal is not approvable as 

submitted. The submission is also not 

clear about whether the new opacity 

standard for certain sources with COMS 

at 335–3–4–.01(3)–(5) applies in 

addition to, or in lieu of, the existing 

opacity standard in paragraphs 335–3–

4–.01(1)(a)–(b), as measured under 

paragraph 335–3–4–.01(2). In addition, 

the purpose behind new paragraph 335–

3–4–.01(5) is not clear. 

EPA believes the State can revise the 

2003 ADEM submittal by amending it to 

ensure that the allowable average 

quarterly opacity is at least as stringent 

as (i.e., equal to or lower than) that 

allowed by the current approved SIP, 

and by being clear that only a single 

version of the standard applies to any 

unit (although any credible evidence of 

opacity could be used to assess 

compliance with the applicable version 

of the standard). Accordingly, this 

proposed approval is contingent upon 

Alabama’s submission of a revised rule 

with certain changes. The revision 


rmajette on PROD1PC67 with PROPOSALS
Federal Register / Vol. 72, No. 70 / Thursday, April 12, 2007 / Proposed Rules 18431 

4As noted elsewhere, the exemptions in 

paragraphs 335–3–4–.01(1)(c)–(e) are not impacted 

by the 2003 SIP revision and would continue to 

apply to either the existing or the revised standard. 

5Although this new opacity standard would only 

apply to certain sources using COMS, EPA notes 

that, consistent with EPA’s and ADEM’s credible 

evidence rules, nothing in the rule should preclude 

the use of COMS to enforce the existing standard 

or the use of Method 9 to enforce the new standard. 

6The director’s discretion provisions under 

Alabama rule 335–3–4–.01(1)(c) and (d) would be 

unchanged by this SIP revision, so periods of excess 

emissions allowed in a permit pursuant to those 

provisions would continue to be allowed, in 

addition to the emissions allowed by the new 

provisions discussed herein. EPA notes that, as the 

director’s discretion provisions are not being 

revised by ADEM or reviewed by EPA at present, 

nothing in this notice should be considered as 

approving those provisions. 

would clearly indicate that a unit is 

covered by either the existing opacity 

standard at paragraphs 335–3–4–

.01(1)(a)–(b), as measured under 

paragraph 335–3–4–.01(2), or by the 

new standard established in paragraphs 

335–3–4–.01(1)(a), (3)–(4), as measured 

by the COMS referenced in those 

paragraphs—but not both.4 The revision 

would also provide that the hourly 40 

percent exemption under Alabama rule 

335–3–4–.01(1)(b) does not apply to 

sources subject to the new paragraphs 

335–3–4–.01(3) and 335–3–4–.01(4). 

Thus, the 40 percent exemption for up 

to 24 six-minute periods per day on an 

hourly basis would be replaced by the 

generally applicable 20 percent 

standard. The revision would allow a 

source to exceed the 20 percent 

standard (up to 100 percent opacity) 

during no more than 24 six-minute 

periods per day. In part this revision 

would replace the existing provision 

allowing one six-minute exceedance per 

hour at 40 percent opacity with a 

provision allowing up to 24 six-minute 

exceedances per calendar day at 100 

percent opacity. However, under the 

revised provision, these exceedances 

would be part of, not in addition to, the 

exceedances allowed under 335–3–4–

.01(4) (i.e., two percent of operating 

time). 

Thus, under the current SIP, a source 

is required to maintain 20 percent 

opacity, except that it may emit at up to 

40 percent opacity for one six-minute 

average per hour, and may have 

emissions of up to 100 percent opacity 

as specified in a permit. Under the 2003 

submission, certain sources using 

COMS would, in addition to the current 

SIP exemptions, also be allowed 

emissions of up to 100 percent opacity 

for up to two percent of the quarterly 

operating time that they are otherwise 

subject to the 20 percent opacity limit. 

Under the revision proposed for 

approval in this notice, these sources 

still would be allowed emissions of up 

to 100 percent opacity for up to two 

percent of quarterly operating time that 

they are subject to the 20 percent 

opacity limit (but not to exceed 10 

percent of a calendar day), and they 

would not be allowed the 40 percent 

hourly exemption.5

Where currently any source may 

exceed the opacity limit for six minutes 

out of every hour (i.e., 10 percent of the 

time, on an hourly basis), under the 

revision EPA is proposing would be 

approvable, a source using COMS 

subject to the new standard could 

exceed the opacity limit for 10 percent 

of the time on a daily basis (i.e., up to 

2.4 hours of consecutive opacity 

exceedances per calendar day), but for 

only two percent of the time on a 

quarterly basis. Under the current 

standard, the 40 percent opacity limit in 

theory allows a source to emit a total of 

approximately 219 hours of emissions 

in a quarter at up to 40 percent opacity, 

if the source uses one six-minute 

exemption for every hour of operation. 

Under the proposed revision, a source 

would be allowed to emit no more than 

44 hours of excess emissions in a 

quarter (and no more than 2.4 hours in 

a day), but those emissions could have 

up to 100 percent opacity.6

As a result, the final rule would have 

the potential to increase the impact of 

opacity exceedances on a short-term 

basis by allowing exceedances of up to 

100 percent opacity and also allowing 

those periods of excess opacity to be 

aggregated in up to 24 consecutive sixminute periods per day (as opposed to 

the current approved rule which 

provides an hourly 40 percent 

exemption, also for a total of 24 sixminute periods per day). However, the 

long-term cap of two percent serves to 

restrict the total amount of time a source 

is allowed to exceed the standard. As 

discussed below, EPA believes that the 

reduction in total duration of 

exceedances will reduce average opacity 

as compared to the current standard, 

even taking into consideration that the 

exemption in the current standard limits 

exceedances to 40 percent (not 100 

percent) opacity. 

Thus, under the proposed revised 

rule, with the changes discussed in this 

notice, an emissions unit covered by the 

new standard would be allowed: (1) Up 

to 100 percent opacity during periods of 

startup, shutdown, load change, and 

rate change or other short, intermittent 

periods upon terms approved by 

ADEM’s Director and included in a 

state-issued permit; (2) up to 100 

percent opacity for up to two percent of 

the operating time on a quarterly basis 

(where the amount of operating time 

does not include the exempted periods 

approved by ADEM’s Director and 

included in a state-issued permit), but 

for no more than ten percent of the time 

on a daily basis; and (3) up to 20 percent 

opacity for the rest of the time in a 

quarter. The current federally-approved 

SIP opacity limit remains in effect. Any 

new exceptions proposed in this action 

do not take effect until EPA takes final 

action. Furthermore, any final rule 

would be prospective only. In addition, 

this proposal is not intended to affect 

on-going enforcement actions against 

sources that may be subject to the new 

standard, nor does it relieve affected 

sources in Alabama of their obligations 

to comply with any other federal, state, 

or local opacity requirements, or 

particulate matter control requirements. 

VI. What Technical Analysis Was Used 

To Support Approval of This SIP 

Revision? 

The existing Alabama SIP specifies 

Method 9 as the method for determining 

compliance with the generally 

applicable opacity limit for sources of 

PM emissions. See Ala. Admin. Code r. 

335–3–4–.01(2). More frequent readings 

with COMS help determine whether a 

source is following good air pollution 

control practices between Method 9 or 

Method 5 tests. With the additional 

restrictions described above, the 

proposed SIP revision can be shown to 

be no less stringent in terms of average 

quarterly opacity than the existing SIP. 

Today, we propose to approve 

Alabama’s SIP revision contingent upon 

the revision including our 

recommended changes, based on a 

finding that the revision would not 

increase average quarterly opacity levels 

and thus would not interfere with 

attainment or maintenance of a NAAQS, 

RFP, or any other requirement of the 

Act. The relationship between changes 

in opacity and increases or decreases in 

ambient PM2.5 levels cannot be 

quantified readily and is particularly 

uncertain for short term and sitespecific analyses. There are several 

contributors to this uncertainty 

including (1) differences between 

combustion technology characteristics 

and fuel components, (2) differences in 

control technology types, temperatures 

at which they operate, and load 

characteristics, (3) the recognition that 

both opacity and mass emissions are 

subject to significant variability over 

short periods of time and fluctuations in 

one may not track fluctuations in the 

other, and (4) differences between what 

the ambient sampler collects and the 

mass of particles that exists at the point 


rmajette on PROD1PC67 with PROPOSALS
18432 Federal Register / Vol. 72, No. 70 / Thursday, April 12, 2007 / Proposed Rules 

of COMS measurement (e.g., in the 

stack) and the direct PM2.5 that forms 

immediately upon exiting the stack (that 

are related to fuel components more 

than to control technology). 

In addition to these uncertainty 

factors, opacity is directly related to 

particle size, with particles of an 

aerodynamic diameter of approximately 

1.0 micrometer having the greatest 

potential for impairment of visibility, or 

increased opacity. (See, e.g., Malm, 

William C. ‘‘Introduction to Visibility,’’

Cooperative Institute for Research in the 

Atmosphere, May 1999, Chap. 2, p. 8). 

As particles increase in size, their 

impact on opacity diminishes, despite 

the fact that their mass may increase. 

Thus for PM emissions of a given mass 

level, opacity can be greater or less 

depending on the particle size 

distribution. 

Several past instances and State and 

Federal rules are instructive regarding 

the uncertainties in relating opacity to 

PM concentrations. EPA recognized and 

accounted for these uncertainties as 

early as the 1970s by permitting sources 

to adjust source-specific opacity 

standards under new source 

performance standards (NSPS) when 

they could demonstrate that they were 

in compliance with applicable PM 

limits at times when opacity limits were 

being exceeded. See, e.g., 44 FR 37960, 

37961 (June 29, 1979). In EPA’s own 

NSPS for glass manufacturing plants, 

(40 CFR 60.293(e)), and national 

emission standard for Inorganic Arsenic 

Emissions from Glass Manufacturing 

Plants (40 CFR 61.163), EPA has written 

specific provisions into its standards 

permitting source owners or operators to 

redetermine opacity limitations where 

they can demonstrate compliance with 

emission limits in the applicable rules. 

More recently, when examining a study 

of COMS at a portland cement kiln, we 

have found that the plant’s visible 

emissions readings were consistently 

below its allowable limit (20 percent) 

while PM emissions significantly 

exceeded the NSPS due to broken bags 

in its baghouse. Finally, a number of 

States have incorporated similar 

provisions into their regulations. (See, 

e.g., Indiana Administrative Code, 326 

IAC 5–1–5(b); Wisconsin NR 431.07; 

Pima County, Arizona 2–8–300(C)). 

The contributions to uncertainty 

described above lessen when applied to 

longer term averages and the 

relationship between ambient PM2.5

measurements and changes in opacity 

are more reliable than for shorter term 

(e.g., daily) assessments. Therefore, for 

purposes of this proposal, EPA focused 

on analyzing the effects of the proposed 

change in the opacity limitations for 

facilities covered by the rule over 

quarterly periods. EPA believes that a 

quarterly basis is appropriate because 

correlations between opacity and PM 

control device operation are more 

readily generalized over a longer-term 

basis and, therefore, a quarterly average 

is more likely to reflect impacts on the 

ambient PM levels accurately than a 

daily average, and because ADEM’s 

proposed rule includes a quarterly limit. 

By calculating and comparing the 

average quarterly opacities allowed by 

the current SIP approved rule, the 2003 

ADEM submittal, and the 2003 ADEM 

submittal with required changes 

specified, we can determine which 

proposed SIP change, if any, provides 

an average quarterly opacity equivalent 

with, or more stringent than, the average 

quarterly opacity allowed by the current 

SIP approved rule. Proposed changes 

that provide average quarterly opacities 

more stringent than (or equivalent with) 

those allowed by the existing SIP rule 

are expected to be more stringent than 

(or equivalent to) the existing SIP rule. 

EPA is not performing similar 

calculations comparing stringency of 

average daily opacity levels under the 

current rule and the proposed rule 

because a generally applicable 

relationship between opacity and PM 

mass emissions cannot be specified over 

short averaging times (e.g., 24 hours or 

less). Even with extensive testing, it is 

very difficult to establish reliable 

correlations between the magnitude of 

opacity measurements and PM mass 

emissions for short averaging times (e.g., 

24 hours or less) that will remain 

reliable over a longer period of record 

(i.e., that will establish a direct daily 

correlation over a longer period, such as 

three or more months). Therefore, 

opacity may not be a reliable indicator 

of short-term emissions, or for use in 

projecting changes in short-term PM 

ambient air quality concentrations. 

Accordingly, we conclude that the 

proposed change in the allowed opacity 

will have no effect on attainment of the 

24-hour PM NAAQS (35 μg/m3 for PM2.5

and 150 μmg/m3 for PM10) or (based on 

the quarterly stringency comparison) the 

annual PM NAAQS (15.0 μg/m for 

PM2.5). 

We can calculate the average 

allowable quarterly opacity for a unit by 

multiplying an allowed level of opacity 

by the duration for which that level of 

opacity is allowed, summing those 

products for each allowed level of 

opacity occurring over a quarter, and 

then dividing that total by the number 

of six-minute periods in a quarter. The 

average quarterly opacity for a unit is an 

opacity value equivalent with one 

single, constant opacity value emitted 

for each and every six-minute period of 

the quarter, allowing us to compare a 

unit with a longer period of lower 

opacity to one with a shorter period of 

higher opacity. 

The general formula for calculating 

the allowable average quarterly opacity 

(i.e., the average opacity (percent) 

allowed by rule over a quarter) is: 

Allowable

opacity duration n n

 average quarterly opacity =

( ) ∗( ) i

n

=

∑1

21 900 ,

Where: 

n = specific period of quarterly operation, 

opacity = opacity (percent) related to that 

specific period, 

duration = number of six-minute average 

periods related to the specific period, 

and 

21,900 = number of six-minute average 

periods per quarter. 

For the Alabama analysis, using the 

above general formula to determine the 

allowable average opacity over a 

quarter, we chose to use the maximum 

opacity allowed for each condition, the 

maximum duration allowed for each 

condition, and the maximum amount of 

time for unit operation when calculating 

the average allowable quarterly opacity. 

Although operation with opacity at the 

maximum level for the longest period 

allowed under a rule is not reflective of 

actual operations, such a conservative 

assumption provides a consistent basis 

for comparisons. 

Usually calculation of allowable 

average quarterly opacity can be readily 

ascertained, since opacity limits and 

their associated condition durations are 

known explicitly. However, because 

ADEM allows an exemption from 

opacity limits during periods of startup, 

shutdown, load change and rate change 

or other short, intermittent periods upon 


rmajette on PROD1PC67 with PROPOSALSEP12AP07.010</MATH>
Federal Register / Vol. 72, No. 70 / Thursday, April 12, 2007 / Proposed Rules 18433 

7EPA does not intend to indicate that it would 

be appropriate or consistent with the SIP for an 

exemption period under 335–3–4.01(1)(c) to last for 

an extended period of time, but rather is utilizing 

conservative assumptions for the purpose of 

ensuring the requirements of section 110(l) will be 

met. EPA does not anticipate that a source would, 

in fact, operate at 100% opacity for all permissible 

excursion periods. 

terms approved by ADEM’s Director and 

included in a state-issued permit, and 

because the duration of those periods is 

not known, we used a variable, T1, to 

represent the duration of those periods. 

In theory, the duration of those periods 

could range from 0, meaning no periods 

of exemption for a quarter, to 21,900, 

meaning all periods of the quarter are 

exempt.7 In practice, one sample of 

units subject to the current SIP rule 

contains durations of about 400 periods 

per quarter for this exemption. 

Relying on the variable T1, calculation 

of allowable average quarterly opacities 

becomes straightforward. By way of 

example, the allowable average 

quarterly opacity for the 2003 ADEM 

Submittal is the sum of the ten percent 

of the quarter’s duration at 40 percent 

opacity, the time (T1) at 100 percent 

opacity due to exemptions, the two 

percent of the non-exempt time of the 

quarter’s duration at 100 percent 

opacity, and the balance of the nonexempt time of the quarter’s duration at 

20 percent opacity, all divided by the 

number of six-minute periods in the 

quarter. The equation shown below 

provides the allowable average quarterly 

opacity for the 2003 ADEM Submittal 

for T1 values of 0 to 19,710: 

Allowable average quarterly opacity =





 



∗ 



 



21 900

10

40 ,  + ∗ ( ) + −− 



 



∗ ∗ 



 



 T T 1 1 100 21 900 +

21 900

10

2

100 , 100 21 900 , , − − 



 



∗ ∗ 



 





























⋅

21 900

10

98

100

20

21 900

1

,

,

T

We derived allowable average 

quarterly opacity equations for the 

current SIP-approved rule and the 2003 

ADEM submittal, substituted various 

exemption durations (T1) in the 

equations, determined the 

corresponding allowable average 

quarterly opacities, and organized the 

results as shown in Table 1 below. 

TABLE 1.—CALCULATED ALLOWABLE AVERAGE QUARTERLY OPACITY LEVELS, FOR VARIOUS STARTUP, SHUTDOWN, LOAD

CHANGE, AND RATE CHANGE DURATIONS (T1), USING ALABAMA’S CURRENT SIP-APPROVED RULE, AND THE 2003 

ADEM SUBMITTAL

Calculated allowable average quarterly opacity (percent) for various startup, shutdown, load change and rate change durations (T1) 

T1 = 0 T1 = 1,000 T1 = 10,000 T1 = 17,520 T1 = 19,710 T1 = 21,900 

Current SIP Approved Rule ............................................. 22.00 25.65 58.53 86.00 94.00 100.00 

2003 ADEM Submittal ..................................................... 23.44 27.02 59.24 86.16 94.00 100.00 

As can be seen, under these 

conservative assumptions, the 2003 

ADEM submittal would result in 

allowable average quarterly opacity 

levels that are slightly higher than those 

calculated from the current SIP rule for 

periods of startup, shutdown, load 

change and rate change, i.e. for where 

those durations are less than 19,710 sixminute averages. 

In order to be approvable, we have 

recommended that ADEM eliminate the 

exemption for six-minutes at up to 40 

percent opacity for up to ten percent of 

the operating time. The allowable 

average quarterly opacity for the 2003 

ADEM Submittal With Required 

Changes Specified for all T1 values = 

TT T 11 1 100 21 900 2

100

100 21 900 98

100 ( ) ∗ + − ( ) ∗ ∗ 20 



 



 + − ( ) ∗ ∗ 

 , ,  





























⋅ 21 900 ,

We derived allowable average 

quarterly opacity equations for the 

current SIP approved rule and the 2003 

ADEM submittal with recommended 

changes specified, substituted various 

exemption durations (T1) in the 

equations, determined the 

corresponding allowable average 

quarterly opacities, and organized the 

results as shown in Table 2 below. As 

shown, the proposed revision to the SIP 

rule yields an allowable average 

quarterly opacity equivalent to or less 

than the allowable average quarterly 

opacity calculated from the current SIP 

rule in all cases. 


rmajette on PROD1PC67 with PROPOSALSEP12AP07.011</MATH> EP12AP07.012</MATH>
18434 Federal Register / Vol. 72, No. 70 / Thursday, April 12, 2007 / Proposed Rules 

TABLE 2.—CALCULATED ALLOWABLE AVERAGE QUARTERLY OPACITY LEVELS, FOR VARIOUS STARTUP, SHUTDOWN, LOAD

CHANGE, AND RATE CHANGE DURATIONS (T1), USING ALABAMA’S CURRENT SIP-APPROVED RULE AND THE PROPOSED SIP REVISION WITH RECOMMENDED CHANGES SPECIFIED

Calculated allowable average quarterly opacity (percent) for various startup, shutdown, load change and rate change durations (T1) 

T1 = 0 T1 = 1,000 T1 = 10,000 T1 = 17,520 T1 = 19,710 T1 = 21,900 

Current SIP Approved Rule ............................................. 22.00 25.65 58.53 86.00 94.00 100.00 

2003 ADEM Submittal with Recommended Changes 

Specified ....................................................................... 21.60 25.18 57.40 84.32 92.16 100.00 

Therefore, by incorporating these 

recommended changes, Alabama would 

reduce uncertainties related to whether 

such a change could interfere with 

attainment, RFP or any other 

requirement of the Act. Accordingly, we 

conclude that the revision of Alabama’s 

SIP rule to incorporate the 2003 ADEM 

submittal with our recommended 

changes specified in this action would 

not interfere with requirements of the 

CAA and would be approvable. Further 

details of this analysis are contained in 

the technical support document. 

VII. What Happens Next? 

EPA anticipates Alabama will submit 

a revised rule revision reflecting the 

changes discussed in section IV above. 

If Alabama’s revised rule is submitted 

and considered approvable, after 

considering any comments received on 

today’s proposed approval, EPA will 

publish a final rule in the Federal 

Register approving the State’s requested 

rule revision and will also address in 

that rulemaking any comments received 

on this proposed approval. In addition, 

we plan to develop further criteria to aid 

EPA Regional Offices in evaluating 

future revisions to rules such as 

Alabama’s and, in this regard, we expect 

to publish in the near future a request 

for information that will assist us in that 

effort. 

VIII. Proposed Action 

EPA is proposing to approve the 

Visible Emissions portion of a SIP 

revision submitted to EPA by Alabama 

on September 11, 2003, provided it is 

revised as described in section IV of this 

action and submitted as a SIP revision 

in accordance with the requirements of 

the CAA. 

IX. Statutory and Executive Order 

Reviews 

Under Executive Order 12866 (58 FR 

51735, October 4, 1993), this proposed 

action is not a ‘‘significant regulatory 

action’’ and therefore is not subject to 

review by the Office of Management and 

Budget. For this reason, this action is 

also not subject to Executive Order 

13211, ‘‘Actions Concerning Regulations 

That Significantly Affect Energy Supply, 

Distribution, or Use’’ (66 FR 28355, May 

22, 2001). This proposed action merely 

proposes to approve state law as 

meeting Federal requirements, and 

imposes no additional requirements 

beyond those imposed by state law. 

Accordingly, I hereby certify that this 

proposed rule will not have a significant 

economic impact on a substantial 

number of small entities under the 

Regulatory Flexibility Act (5 U.S.C. 601 

et seq.). Because this action proposes to 

approve requirements under state law 

and does not impose any additional 

enforceable duty beyond that required 

by state law, it does not contain any 

unfunded mandate or significantly or 

uniquely affect small governments, as 

described in the Unfunded Mandates 

Reform Act of 1995 (Public Law 104–4). 

This proposed rule also does not have 

tribal implications because it will not 

have a substantial direct effect on one or 

more Indian tribes, on the relationship 

between the Federal Government and 

Indian tribes, or on the distribution of 

power and responsibilities between the 

Federal Government and Indian tribes, 

as specified by Executive Order 13175 

(65 FR 97249, November 9, 2000). This 

proposed action also does not have 

Federalism implications because it does 

not have substantial direct effects on the 

States, on the relationship between the 

national government and the States, or 

on the distribution of power and 

responsibilities among the various 

levels of government, as specified in 

Executive Order 13132 (64 FR 43255, 

August 10, 1999). This action merely 

proposes to approve State rule as 

consistent with Federal standards, and 

does not alter the relationship or the 

distribution of power and 

responsibilities established in the CAA. 

This proposed rule also is not subject to 

Executive Order 13045, ‘‘Protection of 

Children from Environmental Health 

Risks and Safety Risks’’ (62 FR 19885, 

April 23, 1997), because it is not 

economically significant. 

In reviewing SIP submissions, EPA’s 

role is to approve state choices, 

provided that they meet the criteria of 

the CAA. In this context, in the absence 

of a prior existing requirement for the 

state to use voluntary consensus 

standards (VCS), EPA has no authority 

to disapprove a SIP submission for 

failure to use VCS. It would thus be 

inconsistent with applicable law for 

EPA, when it reviews a SIP submission 

to use VCS in place of a SIP submission 

that otherwise satisfies the provisions of 

the CAA. Thus, the requirements of 

section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (15 U.S.C. 272 note) do not 

apply. This proposed rule does not 

impose an information collection 

burden under the provisions of the 

Paperwork Reduction Act of 1995 (44 

U.S.C. 3501 et seq.). 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Carbon monoxide, 

Intergovernmental relations, Nitrogen 

dioxide, Ozone, Particulate matter, 

Reporting and recordkeeping 

requirements, Sulfur oxides, Volatile 

organic compounds. 

Authority: 42 U.S.C. 7401 et seq. 

Dated: April 4, 2007. 

J.I. Palmer, Jr., 

Regional Administrator, Region 4. 

[FR Doc. E7–6948 Filed 4–11–07; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Parts 52 and 81 

[EPA–R03–OAR–2006–0917; FRL–8298–3] 

Approval and Promulgation of Air 

Quality Implementation Plans; Virginia; 

Redesignation of the RichmondPetersburg 8-Hour Ozone 

Nonattainment Area To Attainment and 

Approval of the Associated 

Maintenance Plan and 2002 Base-Year 

Inventory 

AGENCY: Environmental Protection 

Agency (EPA). 


rmajette on PROD1PC67 with PROPOSALS